1. Field of the Invention
The present invention relates to a foldable keyboard with superior portability and good operationality in use and, more particularly, to a foldable keyboard including two keyboard units and a cover member which is turned in synchronization with rotation of each keyboard unit and covers end faces and both side portions of each end face of the keyboard units held in a superposed state.
2. Description of Related Art
Heretofore, there have been proposed various types of foldable keyboards including two separate keyboard units rotatably connected with each other. When the keyboard is not in use, the keyboard units are superposed one on top of the other to bring the keyboard into a folded compact state, thus making it easy to carry anywhere. When in use, on the other hand, the keyboard units are separated to unfold the keyboard into a spread state, thus providing high operationality equivalent to standard keyboards.
However, the above keyboard has the following disadvantages. When the keyboard units rotatably connected with each other are superposed, their end faces (the backsides) are directly exposed. This causes the entry of dirt or the like in the inside of each key switch, leading to operational or mechanical troubles, and also the appearance of the keyboard is deteriorated.
To avoid the above disadvantages, for example, Japanese patent unexamined publication No. 2000-56904 (pages 3–5 and FIGS. 1–12) discloses a foldable keyboard including two separate keyboards at least one of which is slidably supported on a support plate. The separate keyboards are rotatably connected to both sides of a back plate, directly or via the support plate. In this keyboard, when the two keyboards are folded, the back plate covers end faces of the keyboards, like a spine of a book, to prevent dust and waterdrops from entering the keyboards.
Furthermore, U.S. Pat. No. 5,574,481 (second and third columns and FIGS. 2, 7, and 9) discloses a foldable keyboard including two separate keyboard units which are connected to be brought into or out of contact with each other, so that the keyboard units can be folded while they are set apart from each other. In this keyboard, after folding, a cover plate placed slidably to cover both side portions of each end face of the keyboard units. This cover plate is slid and turned to cover the end faces of the keyboard units.
In the former keyboard (JP-A-2000/56904), however, the back plate covers the end faces of the two separate keyboards, whereas it cannot cover over the both side portions of each end face of the keyboards when folded, as shown in FIG. 8 of JP-A-2000/56904.
Similarly, in the latter keyboard (U.S. Pat. No. 5,574,481), the cover plate covers the end faces of the two keyboard units, whereas it cannot cover over the both side portions of each end face of the keyboard units when folded, as shown FIG. 9 of U.S. Pat. No. 5,574,481.
Furthermore, in the former keyboard (JP-A-2000/56904), the two separate keyboards are rotatably connected to both sides of the back plate. Thus, two rotational connecting parts are provided at the sides of the back plate. With this structure, the folding and opening motions of the keyboards tend to be unstable.
In the latter keyboard (U.S. Pat. No. 5,574,481), the two keyboard units have to be mutually folded or horizontally opened while they are set apart from each other. Accordingly, the folding and opening motions of the keyboard units tend to be unstable.
Meanwhile, compact portable devices such as a personal digital assistant (PDA) have remarkably progressed and come into wide use. The compact portable devices of this type, provided with key switches, are of a small body which needs small-sized key switches and others. Thus, the development of a portable keyboard that can be connected with such portable devices has been demanded.
However, the former keyboard (JP-A-2000/56904) in which the two separate keyboards are rotatably connected with the both sides of the back plate so as to be foldable has been proposed without consideration of the connection of the keyboard with the compact portable devices such as a PDA.
The latter keyboard (U.S. Pat. No. 5,574,481) also has been proposed without consideration of the connection of the keyboard with the compact portable devices such as a PDA.